Thomas evans



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THOMAS EVANS, 0E NEWARK, NEW JERSEY. Letters .Patent No. 71,595, datedDecember 3, 1867.

IMPROVEMENT IN DRAUGHTIG-INSTRUMENT.

Be it known that I, THOMAS EVANS, of Newark, Essex county, New Jersey,have invented a new and useful Tool for the use of Tinners and otherArtisans; and I do hereby declare that the following is a full and exactdescription thereof, reference being had t0 the annexed drawings.

Figure 1 is an edge view ci' the tool.

Figure 2 is a. front or, full view.

l I Figure 3 is a plan of bar g.

Figure 4 is a development of a conical frustum.

My invention consists of a square, a, graduated on the edges, combinedwith a sliding bar, g, arranged to move freely along one arm of thesquare a and stand-at right angles therewith; A straight-edge, b, isclamped tothe b'ar g by a thumb-nut or screw, f, and hield in contactwith the other arm of the square a by the piecetz,

fastened to the straight-edge and pinchingthe arm 7c of the square a.These three pieces a, g, and 6, can be, moved into various positions;and, when'the sliding bar g is set at a distance from the base kof thesquare a equal to the height of the desired frustum of -a cono, and thestraight-edge bis set with its' one end intcry secting the graduationson the arm k at a point indicating the semi-diameter of the larger endof said frustum, and its edge intersecting the bar g at a pointindicating thereonthe semi-diameter of the smaller end of said frustum,the gradual-tions on the straight-cdge Z1, from its foot to itsintersection with the bar g, will indicate the slant height of thefrustum, and the distances from m to a and from n to o will representthe correct radius to be employed in developing the surface of the frustum on a plane surface. This property of the tool gives it a greatdegree of usefulness where any one (as a tinner) is frequently employedin cutting sheet metal onpaper to fit conical or pyramidal surfaces.

I The tool isrepresented in the drawings as properly set to lay-out a1amp-shade of conical form, ten 'inches diameter across the bottom, fourinches across the top, and four and a half in height. `The graduationson the straight-edge'from m to n show that the slant heightis five andthree-eighth inches, that the radius from m to o is nine inches, and theradius freni n to o is three and tive-eighth inches. The development ofthe shade in a plane'surface is shown in iig-4, drawn one-fourth of thefull size in inches.

-When the proportions of a igure larger than the tool are required, theycan be obtained by setting the tool to one-half` of the dimensionsrequired, or one-third or fourth, as the case may need. Thus, the toolcan be'made to serve the place of a large stock of tinners patterns.

The bar g is slotted, as Well as the straight-edge b, to afford facilityof adjustment; anda piece is secured at its end by a. thumb-screw,f, inthe slot of b. This piece has a scriber, d, fastened at its extreme end,which renders it capable, when used in conjunction with the scriber z'at the foot of b, of serving as Compasses, snpposing the pieces'b and cto be detached from the square a and bar g. Thielinstrument, therefore,combines a square, straight-edge, compasses or scriber, severalmeasuring-scales, andfa tool for describing geometrical figures in apractical manner. `It thus affords a new and useful instrument forsmiths, metal-workers, shipwrights, millwrights, carpenters, &c.

What I claim as new, and desire to secure by Letters Patent, is-

1. The combination of the scalc-rules b and g with the square a, madeadjustable thereon, substantially as set forth.

2. The arm-c, in combination with the slotted straight-edge b, cachbeing provided with a point, d z, and.'

made adjustable with relation to each other, substantially as and forthe purposeset forth.

THOS. EVANS.

Witnesses:-

T. S. CRANE, F. A. EVANS.

